PSN-L Email List Message
Subject: Re: distortion on geophones
From: "tdick" dickthomas01@.............
Date: Mon, 28 Jun 2004 12:37:11 -0500
> Tom,
>=20
> This looks like an electrical problem rather then a problem with the =
sensor.
> Is the signal from the sensor going through one of my Amp/Filter =
boards? If
> it is you may want to send it back to me so I can check it out.
Larry I got several comments that changed my thinking and you may be =
right. I originally thought it was water in the bottom of the hole that =
the geophones were buried in. The geophones are in a 3x3 block of wood, =
in a 4 inch PVC pipe sealed on both ends and about four feet down -- =
very near the surface level of a lake 15 ft away. I noticed the problem =
about the time the rains started here in early April . But I was =
concentrating on local stuff. About that time I also changed my =
filtering -- trying to get a better display for a Internet site. Last =
night the two earthquakes- Illinois & Alaska showed an interesting =
contrast.=20
See all six Alaska and Illinois unfiltered =
http://Dad.bachcottage.com/June 28/raw pics&data . The more intense =
Illinois quake seems more distorted, even on the homemade vertical and =
Lehman's while not so on the Alaskan quake. If I am doing the filtering =
right, it seems to filter out on the homemade vertical and Lehman's -- =
see files unfiltered-filtered in same folder. If you have time, look =
over this folder -- and any other stuff on this disk you have time -- I =
even enclosed raw data and individual event files. All electronics are =
yours. I did remove the jumpers on the amp board.
> Tom,
>
> This looks =
like an=20
electrical problem rather then a problem with the sensor.
> Is the =
signal=20
from the sensor going through one of my Amp/Filter boards? If
> it =
is you=20
may want to send it back to me so I can check it out.
Larry I got =
several=20
comments that changed my thinking and you may be right. I originally =
thought it=20
was water in the bottom of the hole that the geophones were buried in. =
The=20
geophones are in a 3x3 block of wood, in a 4 inch PVC pipe sealed on =
both ends=20
and about four feet down -- very near the surface level of a lake 15 ft =
away. I=20
noticed the problem about the time the rains started here in early April =
..=20
But I was concentrating on local stuff. About that time I also =
changed my=20
filtering -- trying to get a better display for a Internet site. Last =
night the=20
two earthquakes- Illinois & Alaska showed an interesting =
contrast.=20
See all six Alaska and =
Illinois=20
unfiltered http://Dad.bachcottage.com/June=20
28/raw pics&data . The more intense Illinois quake seems more =
distorted,=20
even on the homemade vertical and Lehman's while not so on the Alaskan =
quake. If=20
I am doing the filtering right, it seems to filter out on the homemade =
vertical=20
and Lehman's -- see files unfiltered-filtered in same folder. If you =
have time,=20
look over this folder -- and any other stuff on this disk you have =
time=20
-- I even enclosed raw data and individual event files. All =
electronics are=20
yours. I did remove the jumpers on the amp board.
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